[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Arthropod vectors](https://durgical.com/en/microbiology/groups/arthropod-vectors/) › Glossina, Chrysops and Tabanus

# Glossina, Chrysops and Tabanus

- Parasite
- Exam priority: medium

Large day-biting African flies. Tsetse flies carry sleeping sickness; Chrysops deer flies carry the eye worm Loa loa.

Updated Nov 13, 2026

Also called: tsetse flies, horse flies, deer flies, mango flies

## Quick facts

**Type**
Parasite · [Arthropod vectors](https://durgical.com/en/microbiology/groups/arthropod-vectors/)

**Gram / shape**
Tsetse

**Spread**
Tsetse · Chrysops

**Causes**
Human African trypanosomiasis · Loiasis · Tularaemia

**Treatment**
Does not apply to the insect

On this page

- The basics Key points
- At a glance
- Morphology
- Transmission
- Life cycle
- In Colombia
- Memory aid
- What the colours mean

- Clinical Virulence factors
- Diseases it causes
- Clinical picture
- Diagnosis

- Treatment Treatment
- Prevention

- Study Test yourself

- Connections Connections

## Key points

- Tsetse (Glossina): only vector of sleeping sickness; both sexes bite, by day.
- Tsetse give birth to a single mature larva (no egg-laying), so populations grow slowly.
- Trypanosomal chancre at the bite site, mainly T. b. rhodesiense.
- Chrysops (deer or mango fly) carries Loa loa; blood is drawn around midday.
- Deer fly bites can transmit tularaemia.

## At a glance

**Shape**
Tsetse: brown fly whose wings fold flat over the back like closed scissors, with a forward-pointing proboscis; tabanids: stout flies with large, often coloured eyes

**Family**
Glossinidae (tsetse); Tabanidae (Chrysops, Tabanus)

**Type**
Blood-feeding dipteran insects (biological and mechanical vectors)

**Size**
Tsetse about 1 cm; horse flies up to a few centimetres

## Morphology

- Tsetse flies have a rigid piercing proboscis and a hatchet-shaped cell in the wing.
- Both male and female tsetse flies take blood.
- Tabanid females have cutting mouthparts that tear the skin and cause a painful bite.

## Transmission

- Tsetse: the fly ingests trypanosomes from an infected person or animal; after about three weeks it injects infective forms in its saliva.
- Chrysops: day-biting females ingest Loa loa microfilariae and later deposit infective larvae on the skin.
- Tabanids and deer flies can also carry some pathogens mechanically on their mouthparts, for example in tularaemia.

**Reservoir:** Humans (T. b. gambiense; Loa loa); Wild and domestic animals, especially cattle and antelopes (T. b. rhodesiense)

**Vector:** Glossina is the only vector of human African trypanosomiasis; Chrysops silacea and C. dimidiata carry Loa loa in the rain forests of West and Central Africa.

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- The tsetse female does not lay eggs: she nourishes one larva at a time inside her uterus.
- She deposits a fully grown larva on shaded soil, which burrows in and pupates within hours.
- The adult emerges weeks later; a female produces only a few offspring in her life, so populations grow slowly.
- In the tsetse, trypanosomes multiply in the midgut, then move to the salivary glands to become infective.
- Tabanids lay egg masses on plants over water or mud; larvae grow in wet soil and pupate there.
- In Chrysops, Loa loa microfilariae become L3 larvae in the thoracic muscles and migrate to the proboscis.

## Virulence factors

- Tsetse bites can leave a trypanosomal chancre at the bite site, especially with T. b. rhodesiense.
- Day-biting habits overlap with farming, fishing and forest work.
- Slow tsetse reproduction makes traps and insecticide-treated targets effective for control.
- Painful tabanid bites interrupt feeding, so the fly moves between hosts and can carry blood mechanically.

## Diseases it causes

- Human African trypanosomiasis (sleeping sickness), carried by tsetse flies [Human African trypanosomiasis (sleeping sickness) →](https://durgical.com/en/conditions/human-african-trypanosomiasis/)
- Loiasis (African eye worm), carried by Chrysops deer flies
- Tularaemia, which can follow deer fly bites [Tularaemia →](https://durgical.com/en/conditions/tularaemia/)

## Clinical picture

- Painful tsetse or horse fly bite; a chancre may form at the bite site within days.
- Sleeping sickness: fever and lymph nodes first, then confusion and disturbed sleep.
- Loiasis: transient Calabar swellings and a worm crossing under the conjunctiva.

## Diagnosis

- Entomology: identifying tsetse by the wing fold and wing cell pattern; tabanids by eyes and wings.
- Patient with sleeping sickness: trypanosomes in chancre fluid, blood, lymph node aspirate or cerebrospinal fluid.
- Loiasis: microfilariae in blood drawn around midday, or the adult worm seen in the eye.

## Treatment

Does not apply to the insect. Sleeping sickness is treated with antitrypanosomal drugs chosen by subspecies and stage (pentamidine, fexinidazole, nifurtimox-eflornithine, suramin, melarsoprol); loiasis with antifilarial drugs, with caution in heavy infections.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

- [Pentamidine](https://durgical.com/en/pharmacology/pentamidine/)
- [Diethylcarbamazine](https://durgical.com/en/pharmacology/diethylcarbamazine/)
- [Albendazole](https://durgical.com/en/pharmacology/albendazole/)

## Prevention

- Tsetse traps and insecticide-treated targets or cloth screens; they work because tsetse breed slowly.
- Neutral-coloured clothing, as tsetse flies are drawn to dark blue and black.
- Long clothes during the day in forest and river areas.
- Active screening and treatment of people in endemic areas to remove the human reservoir.

## In Colombia

Tsetse flies and Loa loa are not found in the Americas; in Colombia they matter for travellers and migrants from Africa.

## Memory aid

Tsetse puts you to sleep, Chrysops puts a worm in your eye: both work the day shift in Africa.

## Test yourself

Think of the answer, then tap the question to see it.

## How does tsetse reproduction differ from that of mosquitoes?

The female does not lay eggs; she nourishes one larva at a time inside her body and deposits it fully grown, so populations grow slowly.

## Which fly transmits Loa loa?

Day-biting deer flies of the genus Chrysops, mainly C. silacea and C. dimidiata.

## Why is blood for Loa loa drawn around midday?

Because its microfilariae circulate in blood mainly during the day, matching the biting time of Chrysops.

## Where do trypanosomes become infective inside the tsetse fly?

In the salivary glands, after multiplying in the midgut; the cycle takes about three weeks.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/glossina-chrysops-and-tabanus/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

## Connections

## Related 4

- [Trypanosoma brucei gambiense and T. b. rhodesiense](https://durgical.com/en/microbiology/trypanosoma-brucei-gambiense-and-t-b-rhodesiense/)
- [Loa loa](https://durgical.com/en/microbiology/loa-loa/)
- [Francisella tularensis](https://durgical.com/en/microbiology/francisella-tularensis/)
- [Simulium and Culicoides](https://durgical.com/en/microbiology/simulium-and-culicoides/)

## Related conditions 2

- [Human African trypanosomiasis (sleeping sickness)](https://durgical.com/en/conditions/human-african-trypanosomiasis/)
- [Tularaemia](https://durgical.com/en/conditions/tularaemia/)

[← Back to the group: Arthropod vectors](https://durgical.com/en/microbiology/groups/arthropod-vectors/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Trypanosomiasis, human African (sleeping sickness)](https://www.who.int/news-room/fact-sheets/detail/trypanosomiasis-human-african-(sleeping-sickness)) (WHO, 2025); [CDC - DPDx - Trypanosomiasis, African](https://www.cdc.gov/dpdx/trypanosomiasisafrican/index.html) (CDC, 2024); [CDC - DPDx - Loiasis](https://www.cdc.gov/dpdx/loiasis/index.html) (CDC, 2024); [About Tularemia | Tularemia | CDC](https://www.cdc.gov/tularemia/about/index.html) (CDC, 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/glossina-chrysops-and-tabanus/